Introduction: Composite resins are the most frequently used direct tooth coloured restorative materials. Their use in the posterior teeth has increased because of their improved mechanical performance and wear resistance. However, marginal leakage is one of the major concerns for composite failures especially in the gingival margins of posterior teeth which leads to subsequent failure of the restoration. So, under magnification good integrity can be ensured by maintaining the ergonomics.

Aim: To compare the effect of magnification on the marginal integrity of proximal composite resin restorations.

Materials and Methods: Non-bevelled proximal slots (4.1x4x2.5) mm were prepared on the mesial surfaces of extracted mandibular first molars (N=40) for this in vitro study conducted over a period of one week in the Department of Conservative Dentistry and Endodontics at Army College of Dental Sciences, Secunderabad, Telangana, India. The teeth were randomly divided into two groups (n=20) based on the use of magnification: Group1, direct vision and Group 2, magnification with dental operating microscope. After establishing proximal contacts, the slots were restored with composite resin (Tetric N-Ceram, Ivoclar Vivadent, Mumbai, India) using a sectional matrix system (Palodent Plus Sectional Matrix System Kit, Dentsply, Caulk, US). The margins were analysed using an environmental Scanning Electron Microscope (SEM). The data was statistically analysed using Kruskal–Wallis and Mann–Whitney U tests (p<0.05).

Results: Indicate that the difference in marginal quality of gingival margin was significantly influenced by magnified vision when compared with unaided direct vision (p<0.05). However, the difference was not statistically significant between the groups in relation to buccal and lingual margins. Within the groups, Group 1 showed a higher percentage of gaps in gingival margins as compared to buccal and lingual margins. Whereas, in Group 2, the marginal gaps in both lingual and gingival margins were higher than buccal margins.Conclusion: The marginal integrity of proximal composite restorations can be improved when performed under magnification.